Tracking the position of probes within the body is required for many medical procedures. For example, various systems have been developed for determining the position coordinates of an object in the body based on magnetic field sensing. These systems use sensors affixed to the object to measure the relative strengths of externally-generated magnetic fields and to derive from these measurements the position of the object. Methods for magnetic-based position sensing are disclosed, for example, in U.S. Pat. Nos. 5,391,199, 5,443,489, and 6,788,967 to Ben-Haim, in U.S. Pat. No. 6,690,963 to Ben-Haim, et al., in U.S. Pat. No. 5,558,091 to Acker et al., in U.S. Pat. No. 6,172,499 to Ashe, and in U.S. Pat. No. 6,177,792 to Govari.
The above-mentioned US 2007/0185397 describes methods for generating, storing and computing calibration information with respect to an invasive medical probe, such as a catheter. The probe connects via a suitable mating connector to an adapter, which in turn connects, via another mating connector, to a console. The probe comprises a sensor, such as a magnetic position sensor, and a probe microcircuit, which stores sensor calibration data. The adapter comprises a signal processing circuit for processing the signal that is output by the sensor. The adapter also comprises its own microcircuit, which stores calibration data with respect to the signal processing circuit. A microcontroller in the adapter computes combined calibration data based on the data from both of the microcircuits. Signal analysis circuitry in the console receives the processed signal and analyzes this signal using the combined calibration data provided by the probe adapter.
U.S. Pat. No. 4,290,663, to Fowler et al., describes a method of interconnecting screened cables. This patent states that reduction of magnetic reluctance of the magnetic path between inner and outer surfaces of the screen in the region of the interconnection decreases external interference to the screened cable. Mu-metal can be used to reduce the magnetic reluctance.